Wakesurfing, wakeskating, and wakeboarding involve a rider being towed by a boat or personal watercraft. Once the boat takes off, the rider uses a tow rope to pull him- or herself upright out of the water. For wakesurfing, once the rider gains his balance he releases the rope and surfs the wake. For wakeboarding and wakeskating, the rider continues to hold on to the rope and performs acrobatics while the boat tows him. The size and shape of the wake affect the rider's experience. The size and shape of the wake is in turn affected by the boat shape, size, weight, direction, and speed. It is desirable, therefore, to improve the size and shape of a wake behind a water sport towboat.
Trim tabs are used on boats to compensate for the flow forces that act upon the hull during high-speed travel. By angular adjustment of a trim tab mounted at the stern, the tendency of water drag to impede forward motion can be changed and the handling of the boat improved. More recently, trim tabs have been used to purposefully modify the wake of a boat. One way to do so is to use one or more trim tabs to lift or lower the stern of the boat. Lifting the stern minimizes the wake of a boat, resulting in a relatively smooth water surface, which is desirable for water skiing. Lowering the stern increases the size and changes the shape of the wake, which is desirable for wake riding.
Exhaust gas from motors on towboats is often discharged below the surface of the water to prevent it from asphyxiating those riding in the boat and riding behind it. The location of the motor's exhaust gas outlet is designed to avoid increasing back pressure on the motor, which causes a decrease in motor performance—or kills the motor all together—and to avoid water backing up into the motor through the exhaust piping. Water-cooled inboard engines inject cooling water into the exhaust pipe, which cools the exhaust and muffles engine noise. The exhaust then pushes the water out the exhaust pipe. Forcing exhaust gas and water out below the surface of the water further reduces engine noise.